1. Field of the Invention
The present invention relates to generating an activation code (AC) of a Radio Frequency Identification (RFID) tag, in particular, to record a binary number code having a certain number of bits depending on a number of objects intended to be classified in the AC of the RFID tag, so as to classify the objects through the AC of the RFID tag.
This work was supported by the IT R&D program of MIC/IITA. [2005-S-106-03, Development of Sensor Tag and Sensor Node Technologies for RFID/USN]
2. Description of Related Art
In general, a Radio Frequency Identification (RFID) technology may refer to a technology which may recognize a unique identification of a tagged object via a radio signal to collect, store, process, and trace corresponding information, thereby providing services such as location determination, remote processing, management, information exchange between the tagged objects, and the like with respect to the tagged object. The RFID technology may be applicable to a variety of fields such as materials management, distribution, security, and the like by replacing existing bar code, so that a new market is expected to be formed.
The RFID tag is classified into a passive type when a tag without a battery uses a signal of a reader to generate power, and an active type when a tag with a battery uses a self-contained battery to operate under its own power.
The passive type of tag is comprised of an antenna and a tag chip and the tag chip is comprised of a voltage multiplier, a modulator, a demodulator, a clock generator, a decoder, a controller, an Electrically Erasable Programmable Read-Only Memory (EEPROM) [110], and the like. The voltage multiplier receives an electromagnetic wave through the antenna to generate DC voltage and embodies a configuration circuit of a tag including the EEPROM. However, since a value of the generated voltage is proportional to strength of the electromagnetic wave transmitted from the reader, there is a problem that the passive tag may have difficulty in generating a required voltage when a distance between the reader and the tag is more than a predetermined distance (usually around 5 m).
Conversely, since the tag with a battery is able to be provided with a stable source of electricity using a contained battery, there is an effect that recognition distance extends more than 30 m, unlike the passive tag. However, the life span of the tag is limited to the life span of the contained battery, thus a low power technique to prolong the life span of the battery is required.
Most of circuit of the tag with a battery stays in an inactive state or an idle mode, to prevent unnecessary power consumption, and when a wake-up signal is transmitted from a reader, the whole tag is activated in a short time and then returns to the idle mode after an appropriate amount of time. Accordingly, the circuit for sensing the wake-up signal from the reader is required to be active even when the tag is in an idle mode. Also, since the time of remaining in an idle mode is much longer than that of an active mode, a amount of a stand-by current generated by the circuit is a main factor to determine the life span of the tag.
In the tag with a battery, a reader may transmit an active command including an active mask to the tag, and the tag may identify whether the active mask received from the reader is the same as its own activation mask and determine whether to perform a wake-up.
Currently, International Electrotechnical Commission/International Electrotechnical Commission (ISO/IEC) 18000-6 Rev1.2, one of the committee drafts (CD) of 900 MHz RFID protocol, does not mention a method of generating an activation code (AC). That is, the AC is not a main subject in standardizing a RFID protocol and can be variously defined according to each application.
As is well known, ISO/IEC 18000-6 Rev1.2 does not define a specific standard relating with generating the AC, however, it describes that the AC can be a random value, Unique Item Identifier (UII), or a predetermined portion thereof.
Accordingly, there is a need for a method of generating an AC which can classify object that a user desires to activate using the AC, and activate the classified objects.